The present invention relates to a package for mounting a semiconductor chip therein and also relates to semiconductor device and method for fabricating the device using the package.
First, conventional package and semiconductor device will be described with reference to FIGS. 7(a) and 7(b).
FIGS. 7(a) and 7(b) illustrate conventional package and semiconductor device formed by mounting a semiconductor chip within the package. Specifically, FIG. 7(a) illustrates a planar layout of the assembly yet to be encapsulated, while FIG. 7(b) illustrates a cross-sectional structure of the assembly taken along the line VIIbxe2x80x94VIIb in FIG. 7(a). As shown in FIGS. 7(a) and 7(b), an outer rail 102 made of an insulator is bonded to a radiating plate 101 made of copper. Input lead 103A and output lead 103B pass through the outer rail 102 and are insulated from the radiating plate 101.
As can be seen, the conventional package is made up of the radiating plate 101, outer rail 102 and input and output leads 103A and 103B.
As shown in FIG. 7(b), semiconductor chips 104, in which semiconductor components are formed as power amplifiers, are bonded to the radiating plate 101 of the package with a foil member 105, which may be an alloy containing tin, inside the outer rail 102.
Circuit boards 106 are also bonded to the radiating plate 101 with the foil member 105 inside the outer rail 102. As shown in FIG. 7(a), some of the circuit boards 106 are located between the semiconductor chips 104 and the input lead 103A, while the other between the semiconductor chips 104 and the output lead 103B. Each of these circuit boards 106 includes a matching circuit, which is formed on an insulating substrate to match the input impedance of the semiconductor components with the output one. The semiconductor chips 104, circuit boards 106 and input and output leads 103A and 103B are connected together via wires 107.
In manufacturing the semiconductor device, the semiconductor device assembled as shown in FIGS. 7(a) and 7(b) is heated within a reflow furnace, thereby melting the foil member 105. Thereafter, the assembly is cooled down to room temperature, thereby bonding the radiating plate 101 to the semiconductor chips 104 and to the circuit boards 106.
The conventional semiconductor device using such a package has the following drawbacks. Specifically, when the foil member 105 of an AuSn alloy is heated and melted by the reflow treatment, the melted foil member 105 expands on the radiating plate 101. As a result, the semiconductor chips 104 and the circuit boards 106 are swept by the melted foil member 105 to be displaced from their desired positions.
An object of the present invention is preventing semiconductor chips and so on from being displaced from their desired positions on a support of a package when the chips are being bonded to the support.
To achieve this object, according to an exemplary embodiment of the present invention, a positioning control plate for mounting semiconductor chips at their desired positions is provided over a support of a package. In an alternate embodiment of the present invention, positioning control recesses are provided within the upper surface of the support.
A first exemplary package according to the present invention includes: a support for mounting a semiconductor component on the upper surface thereof; a positioning control plate, which is secured to the support and includes an opening or a notch; and a lead provided on the support for establishing electrical continuity between the semiconductor component mounted on the support and an external component. The positioning control plate houses at least a lower part of the semiconductor component inside the opening or the notch, thereby controlling a position of the semiconductor component on the support.
According to the first package, by housing at least the lower part of the semiconductor component inside the opening or the notch during the fabrication process, the semiconductor component can be positioned on the support with respect to the positioning control plate. Thus, even when the bond member, with which the semiconductor component and the support are bonded together, is melted at the time of heat treatment during the fabrication process, it is possible to prevent the semiconductor component from being displaced laterally on the support. As a result, the production yield can be increased noticeably.
In one embodiment of the present invention, the first package preferably further includes an outer rail, which is secured to the support to enclose the positioning control plate therein. The semiconductor component is preferably positioned on the support with respect to the positioning control plate and the outer rail. In such an embodiment, the positioning control plate need not be provided around the periphery of the package. In addition, the semiconductor component can be encapsulated easily and with a lot more certainty within the package only by hermetically covering the entire periphery of the outer rail with a plate member.
In another embodiment of the present invention, the positioning control plate is preferably formed in such a shape as allowing a melted bond member to pass through corners of the opening or the notch while the semiconductor component is being bonded to the support with the bond member. For example, the sidewalls of the opening or the notch may be partially removed to form recesses at the corners. In such a case, the bond member, which is melted at the time of heat treatment during the fabrication process, does not overflow onto the semiconductor component.
In still another embodiment, the first package preferably further includes a platelike control plate bond member, which is provided between the support and the positioning control plate and includes an opening or a notch in substantially the same shape as that of the positioning control plate. In such an embodiment, the positioning control plate can be bonded onto the support if the heat treatment is conducted approximately at the melting point of the control plate bond member.
A second package according to the present invention includes: a support for mounting a semiconductor component on the upper surface thereof; and a lead for establishing electrical continuity between the semiconductor component mounted on the support and an external component. The support includes a recess for housing at least a lower part of the semiconductor component therein, thereby controlling a position of the semiconductor component on the support.
According to the second package, by housing at least the lower part of the semiconductor component inside the recess during the fabrication process, the semiconductor component can be positioned on the support with respect to the positioning control recess. Thus, even when the bond member, with which the semiconductor component and the support are bonded together, is melted at the time of heat treatment during the fabrication process, it is possible to prevent the semiconductor component from being displaced laterally on the support.
A first semiconductor device according to the present invention includes: a support; a positioning control plate, which is secured to the support and includes an opening or a notch; a semiconductor component bonded to the support in such a manner that at least a lower part of the semiconductor component is housed inside the opening or the notch of the positioning control plate; and a lead provided on the support for establishing electrical continuity between the semiconductor component and an external component.
The first semiconductor device is formed by using the first package according to the present invention. Accordingly, the semiconductor component is not displaced from, but can be bonded at, its desired position on the support, thus increasing the production yield.
In one embodiment of the present invention, the first semiconductor device preferably further includes an outer rail, which is secured to the support to enclose the positioning control plate therein. The semiconductor component is preferably positioned on the support with respect to the positioning control plate and the outer rail.
In another embodiment of the present invention, the positioning control plate is preferably formed in such a shape as allowing a melted bond member to pass through corners of the opening or the notch while the semiconductor component is being bonded to the support with the bond member.
In still another embodiment, the first semiconductor device preferably further includes a platelike control plate bond member, which is provided between the support and the positioning control plate and includes an opening or a notch in substantially the same shape as that of the positioning control plate.
In this particular embodiment, the first semiconductor device preferably further includes a foil member, which is provided between the semiconductor component and the support for bonding the semiconductor component to the support. A melting point of the foil member is preferably lower than that of the control plate bond member. In such an embodiment, if the heat treatment is conducted at a temperature, which is equal to or higher than the melting point of the foil member but lower than that of the control plate bond member, to bond the semiconductor component and the support together, then the control plate bond member is not melted. Accordingly, the positioning control plate is not displaced.
A second semiconductor device according to the present invention includes: a support with a recess formed within the upper surface thereof; a semiconductor component bonded to the support in such a manner that at least a lower part of the semiconductor component is housed inside the recess of the support; and a lead provided on the support for establishing electrical continuity between the semiconductor component and an external component.
The second semiconductor device is formed by using the second package according to the present invention. Accordingly, the semiconductor component is not displaced from, but can be bonded at, its desired position on the support, thus increasing the production yield.
A method for fabricating a semiconductor device according to the present invention includes the steps of: a) securing a positioning control plate, including an opening or a notch, to a support; b) placing a foil member, which is used to bond a semiconductor component onto the support, inside the opening or the notch of the positioning control plate on the support; c) mounting the semiconductor component on the foil member inside the opening or the notch of the positioning control plate on the support such that at least a lower part of the semiconductor component is housed within the opening or the notch; and d) heating the support, on which the semiconductor component has been mounted, to melt the foil member and then cooling down and solidifying the foil member melted, thereby bonding the semiconductor component to the support.
According to the method of the present invention, at least the lower part of the semiconductor component is housed inside the opening or the notch of the positioning control plate on the support when the semiconductor component is mounted on the support in the step c). Thus, even when the foil member is melted in the step d), the semiconductor component can be positioned with respect to the positioning control plate. As a result, it is possible to prevent the semiconductor component from being displaced laterally on the support.
In one embodiment of the present invention, the step a) preferably includes: placing a platelike control plate bond member between the support and the positioning control plate, the bond member including an opening or a notch in substantially the same shape as that of the positioning control plate, a melting point of the bond member being higher than that of the foil member; and heating the support on which the positioning control plate is placed to melt the control plate bond member and then cooling down and solidifying the control plate bond member melted, thereby bonding the positioning control plate to the support. In such an embodiment, since the control plate bond member is not melted in the step d), the positioning control plate is not displaced on the radiating plate.
In another embodiment of the present invention, the foil member is preferably made of an alloy containing gold and tin, and the control plate bond member is preferably made of silver solder with a melting point higher than that of the gold/tin alloy.
In still another embodiment, the step d) preferably includes heating the support with a press member placed on the semiconductor component to prevent the semiconductor component from being warped. In such an embodiment, since the semiconductor component is not warped during the heat treatment, the semiconductor component can be bonded onto the support just as originally designed.